Hi,Thanks for writing to us.There could be multiple causes for spontaneous formation of blisters like insect bite, viral infection, burn, irritant dermatitis and certain autoimmune skin diseases like pemphigoid , pemphigus etc. But a single blister shouldn't be a cause of worry right now. To help the lesion heal just clean the area with warm water and apply an antibiotic cream like mupirocin or fusidic acid or any other OTC antibiotic cream twice in a day. Hopefully in few days the lesion should resolve. Do not remove the scab as it would reveal a raw area underneath and impair faster healing . Let it fall spontaneously.

Hope this helped. Should there be a query, feel free to write back.Regards